1) Field of the Invention
The present invention relates to an apparatus and a process for stirring highly viscous materials, and more particularly to an apparatus for continuous stirring, suitable for continuous polycondensation or stirring, mixing or degassing of polycondensation series polymers (polymer resin) such as polyethylene terephthalate, polycarbonate, etc., and a process for continuous polycondensation of polymer resin.
2) Related Art
Horizontal elongated cylidrical apparatuses for continuous stirring or continuous treatment 8polycondensation, etc.) of polyethylene terephthalate, etc. have been so far disclosed in U.S. Pat. No. 4,776,703 (JP-A-62-112624), JP-A-3-239727 or U.S. Pat. No. 3,964,874 (JP-A-48-102894).
U.S. Pat. No. 4,776,703 discloses an apparatus for continuous treatment of a highly viscous material, which comprises a horizontal elongated cylindrical vessel and two rotating blade assemblies each comprising support rotors provided each at both end walls of the vessel, and a plurality of rectangular frame-shaped rod members connected to one another and spanned between the support rotors, where the adjacent rectangular frame-shaped rod members are connected to one another at a predetermined phase angle in the longitudinal direction of the vessel, thereby making the two rotating blade assemblies rotate in an intermeshed manner without any actual rotating center shaft spanned between the support rotor of the individual rotating blade assemblies.
U.S. Pat. No. 3,964,874 discloses an apparatus for continuous stirring of a viscous material, which comprises a cylindrical vessel, two rotating shafts provided in parallel to each other in the vessel, a plurality of elliptical plate members fixed to the rotating shaft as stirring blades and scraping plates fixed to the outermost ends of the individual elliptical plate members, where the scraping plates are in scraping contact with the entire inside wall of the vessel, thereby minimizing the dead space on the inside wall surface.
In the apparatus of U.S. Pat. No. 4,776,703, the two rotating blade assemblies are each made up of the rectangular frame-shaped rod members, whose adjacent ones are connected to each other at a predetermined phase angle and spanned between the rotor shafts, and thus are suitable for stirring and mixing a liquid feed having a high viscosity, for example, about 1,000 Pa•s or more with less resistance, but in the case of a liquid feed having a lower viscosity than about 1,000 Pa•s, the rectangular frame-shaped rod members only freely pass through the liquid feed without any effective scraping the liquid feed upwards, resulting in failure to promote evaporation of volatile matters and consequent prolongation of residence time.
The apparatus of U.S. Pat. No. 3,964,874 is suitable for stirring and mixing a liquid feed having a low viscosity, but in the case of a liquid feed having a higher viscosity than about a few hundred Pa•s, the stagnant high viscosity liquid feed deposited on the rotating shaft surfaces are liable to rotate together with the rotating shafts, so that the stagnant high viscosity liquid feed are highly susceptible to heat deterioration, etc., resulting in degrading of the quality of the resulting liquid product.